Smoke meter

ABSTRACT

A smoke meter where smoke flows between a light source and a photosensitive element which receives light from the light source, so that the extent to which light is received by the photosensitive element will be influenced by the opacity of the smoke. The light source is electrically connected to a meter which directly gives a reading of the opacity of the smoke. In order to compensate for any fluctuations in light other than the light travelling from the light source to the photosensitive element, a compensating lamp is provided to maintain at the photosensitive element a constant light level by compensating automatically for any fluctuations in light other than the light travelling from the light source to the photosensitive element, so that the latter will respond only to variations in light from the light source to provide an accurate indication of the opacity of the smoke.

United States Patent 1 1 Krukowski 1 1 Jan. 16, 1973 [54] SMOKE METER Primary ExaminerRonald L. Wibert Assistant ExaminerF. L. Evans [76] Inventor: Richard Krukowslu, 39 Maple Street, Chatham NJ 07928 Attorney Harold D. Stemberg et al.

[22] Filed: July 6, 1971 [57] ABSTRACT [21] Appl. No.: 159,595 A smoke meter where smoke flows between a light source and a photosensitive element which receives 52 Us. (:1. ..356/207, 250/205, 250/218, light fmm the extent to which 356/] light is received by the photosensitive element will be 51 Int. Cl. ..G0ln 21/26 influenced by smke- The light [58] Field 0 Search "356/201, 204, 205, 206, 207, source is electrically connected to a meter which 356/208 103, 104; 250/218, 205 directly gives a reading of the opacity of the smoke. In order to compensate for any fluctuations in light other [56] Reerences Cited than the light travelling from the light source to the photosensitive element, a compensating lamp is pro- UNITED STATES PATENTS vided to maintain at the photosensitive element a con- 3 632 209 l/l972 Kingman ..356/207 light level by mPenSating aummatlcally for any 3:524:7O7 1970 Hansen et aL 207 X fluctuations in light other than the light travelling from 3,600,590 8/1971 Einstein ..356/207 the light source to the photosensitive element, so that 1,828,894 10/1931 Freygang.... .....356/103 X the latter will respond only to variations in light from 2,486,622 11/1949 White ..356/l04 the ource to provide an accurate indication of the opacity of the smoke.

12 Claims, 4 Drawing Figures PHOSPHIDE SIUCDN H n PH was} 225 W a it; 4 LENS 52 AMPL'HER FILTER Fou'owm CIRCUIT l V l V l TUNGSTEN CZ'JPELCETD EMTTER I figgti cs ems/N6 AMPJF'ER AMMETER GENERATOR LAMP 6o 74 76 1 46 BATTERY 57 POWER SUPPLY BATTERY HOV CHARGR'R PATENTEDJAH 16 I975 SHEET 2 [IF 2 ATTORNEYS SMOKE METER BACKGROUND OF THE INVENTION The present invention relates to smoke'meters.

As is already known, it is possible to measure the opacity of smoke so as to derive in this way an indication of the extent to which the smoke pollutes the atmosphere. However, up to the present time it has been impossible to achieve accurate reading of the opacity of the smoke. The reason for this is that light-measuring elements respond not only to light directed through the smoke to give an indication of the opacity thereof but also to other light such as ambient or reflected light. For example on bright sunny days a photosensitive element will receive more light than on relatively dark cloudy days, and this variation in ambient light will diminish the accuracy of the measurement of the opacity of the smoke. Furthermore, smoke may have different colors. Smoke can be relatively dark or it may appear white in color. White smoke can be as deleterious to the surrounding atmosphere as dark smoke. However, white smoke will reflect a greater amount of light than dark smoke, and thus the variation in the color of the smoke will provide a further decrease in the accuracy of a measurement of the opacity of the smoke.

SUMMARY OF THE INVENTION It is accordingly a primary object of the present invention to provide a smoke meter which will be capable .of automatically compensating for fluctuations in any light other than the light directed from a light source to a photosensitive element, so that in this way the photosensitive element will respond only to variations in light from the light source, as determined by the opacity of the smoke, to achieve highly accurate readings of smoke opacity, irrespective of such factors as the brightness of the ambient light and the color of the smoke.

A further object of the present invention is to provide a structure of this type which is fully automatic.

Also, it is an object of the present invention to provide a structure of the above type which is portable so that it can easily be carried about and mounted on or removed from a structure from which smoke issues.

In particular, it is an object of the present invention to provide a portable smoke meter which is adapted for use with exhaust pipes of motor vehicles for measuring the opacity of smoke issuing from such an exhaust pipe.

In addition it is an object of the present invention to provide a device of the above type which has a solid state design rendering the structure particularly rugged and suitable for field or laboratory use.

In accordance with the invention a light source means and a photosensitive means are carried by a support means in such a way that light will travel along a predetermined path from the light source means to the photosensitive means to be received thereby. A meter means is provided for giving a direct reading of the opacity of smoke which travels across the path of light between the light source means and the photosensitive means. An electrical means is operatively connected with the photosensitive means and the meter means for providing at the latter a reading of the opacity of the smoke in accordance with the extent to which the light from the light source is influenced by the smoke. Ac-

cording to a particular feature of the invention, a compensating means is carried by the support means and connected to the electrical means to provide at the photosensitive means an automatic compensation for fluctuations in any light other than the light travelling from the light source means to the photosensitive means, so that in this way the photosensitive means will respond only to variations in light from the light source means to give a highly accurate indication of the opacity of the smoke.

BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way of example in the accompanying drawings which form part of this application and in which:

FIG. 1 shows partly schematically an elevation of a smoke meter according to the present invention;

FIG. 2 is a top plan view of that part of the smoke meter which is positioned to receive a stream of smoke;

FIG. 3 is a sectional elevation taken along line 3-3 of FIG. 2 in the direction of the arrows; and

FIG. 4 is a block diagram illustrating the electrical structure of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to FIGS. 1-3, the structure of the invention includes a support means 10 in the form of a suitable open frame. This frame may be of a generally rectangular or square configuration and is made up in the illustrated example of a pair of opposed bars 12 which are parallel to each other and which extend between and are connected to a pair of opposed bars 14 which are also parallel to each other and perpendicular to the bars 12.

The right bar 12 of FIGS. 1-3 is fixed to a downwardly extending bracket 16 pivotally connected to a link 18, and through a suitable bolt and nut 20 it is possible to fix the angle at which the link 18 extends from the bracket 16. This bracket is fixed centrally to the right bar 12 of FIGS. 13.

At its end distant from the bracket 16 the link 18 is pivotally connected to an elongated rod 22 by which the smoke meter may be carried about so that it is highly portable. A bolt and nut assembly 24 is provided at the pivotal connection between link 18 and rod 22 for adjustably fixing the angle therebetween.

The top end of the rod 22 carries an elongated plate 26 to which a substantially U-shaped spring clip 28 is fixed, so that through this spring clip the plate 26 can be located alongside an exhaust pipe 31 shown in phantom lines in FIGS. 1 and 2. Thus, the spring clip 28 will extend into the interior of the pipe 31 around an edge at. the discharge end of the exhaust pipe 31,which may be the exhaust pipe of a motor vehicle, for example, and thus the support means 10 may be positioned in a predetermined manner with respect to smoke issuing from an exhaust pipe 31.

The pair of bars 14 respectively carry plates 30 and 32 between which smoke issuing from the pipe 31 will travel. The plate 30 is formed with openings 34 and 36 shown in FIG. 3. The bar 14 which carries the plate 30 also carries a unit 39 which holds a photosensitive means to which light is directed through the opening 34 and a compensating means from which light issues through the opening 36. The details of the photosensitive means and compensating means are described below.

The bar 14 which carries the plate 32 carries a light source means, also described in greater detail below, and this light source means provides light which issues through a suitable opening in the plate 32. The light from the light source means will travel along the path 38 indicated schematically in dot-dash lines in FIG. 2

from the light source means to the photosensitive means, so that in this way the light from the light source means will be received by the photosensitive means. The light source means is in the form of a unit 40 carried by the bar 14 which carries the plate 32. The support means has a construction which enables the path of light 38 to be situated at approximately 6 inches from the discharge end of an exhaust pipe 30 in the case where the structure is used for measuring the opacity of smoke issuing from the exhaust pipe of a motor vehicle.

Through suitable conductors 42 and 44, which may be partly housed within hollow interiors of the bars 14 and 12, electrical connections are made with an electrical means and a meter means 46. The meter means 46 may be combined with the electrical means in such a way that the meter means 46 will provide a direct reading of opacity of the smoke. For example the needle 48 of the meter may move along a scale 50 which reads from 0 to 100 percent, thus giving an indication of percent of opacity of the smoke.

Referring now to FIG. 4, the light source means 40 is in the form of a gallium phosphide lamp providing through a lens of the lamp light pulses which travel along the path 38 to the photosensitive means 52 in the form ofa silicon photo transistor which is also provided with a lens which receives the light pulses travelling along the path 38. These light pulses provided by the gallium phosphide light source means 40 have a relatively high frequency on the order of 5,000 CPS. For this purpose a suitable pulse generator 54 forms part of the light source means and is operatively connected with the gallium phosphide element so that light pulses 56, indicated schematically in FIG. 4, will travel along the path 38 to the photosensitive means 52 formed by the silicon photo transistor illustrated in FIG. 4.

The pulse generator 54 is provided with energy from a battery power supply 57 provided with suitable batteries such as nickel cadmium batteries of a suitable size, and a battery charger 58 may be connected to the power supply 57 as indicated schematically in FIG. 4.

As was indicated above, the unit 39 includes in addition to the photosensitive means 52 a compensating means to compensate for fluctuations in any light other than the light travelling from the light source means 40 to the photosensitive means 52, and this compensating means is illustrated as a tungsten biasing lamp 60 which will provide light in the space between the plates 32 and 30 through the opening 36 of the plate 30. as described above.

As is indicated in FIG. 4, a very narrow band pass filter 62 is electrically connected to the output from the photosensitive means 52 and is tuned to the 5,000 CPS. The light signals which pass through the band pass filter 62 are amplified by a linear amplifier 64 and then rectified and filtered through the unit 66. The signal from the latter is received by a further amplifier 68 in the form of a voltage follower which provides an output received by the field effect transistor holding circuit 70. This holding circuit 70 has its output connected to the meter 46 which forms that part of the unit which gives a direct indication of the opacity of the smoke. The meter 46 in the illustrated example takes the form of a micro-ammeter, and if desired the output thereof may be recorded as schematically illustrated in FIG. 4.

The above-described electrical means which is connected between the photosensitive means 52 and the meter 46 is also connected electrically with the lamp 60 which forms part of the compensating means. The connection is such that the biasing lamp will maintain a predetermined voltage offset at the output of the photosensitive means 52. Thus, the electrical means includes a direct-coupled amplifier 74 and an emitter-follower 76 connected to the tungsten biasing lamp 60 so as to maintain, in the illustrated example, 1 0.1 volt offset at the output of the photosensitive means 52.

With this construction any stray or reflected light will disturb the 0.1V offset and will automatically rebias the lamp 60 to restore this offset. As a result the photo transistor 52 will always operate at the same light level, insuring maximum linearity and stability. Thus, a very high degree of linearity and insensitivity to ambient light is achieved by electronically biasing the photo transistor light receptor of the smoke meter of the invention.

With the structure of the invention the filtered signal is proportional to the amplitude of the light pulses, so that when there is no light blockage the meter will give a zero reading while when there is a complete light blockage there will be a reading of percent on the meter. Thus, in response to any fluctuations in light other than the light from the light source means 40 the light issuing from the tungsten biasing lamp 60 will vary to maintain a constant light level at the photosensitive means 52. In other words any variations in stray or ambient light, or any variations in reflected light, will be automatically compensated by the tungsten biasing lamp. Any light other than the light from the light source means which becomes brighter than a predetermined level will result in dimming of the biasing lamp 60, while any reduction in the intensity of light other than the light from the light source means will result in automatic brightening of the biasing lamp 60, and the extent to which the light from the biasing lampbecomes dimmer or brighter will be in proportion to the extent to which stray or reflected light becomes brighter or dimmer, degree respectively, so that in this way a fully automatic compensation is achieved in a highly precise manner to maintain all light at the photosensitive means other than the light from the light source means at a constant level, thus achieving a high degreee of precision in the measurement of the opacity of the smoke.

Furthermore, the all solid state design of the structure of the invention provides for a rugged instrument which is ideal for field or laboratory use.

What is claimed is:

l. [n a smoke meter, light source means for directing light along a predetermined path, photosensitive means situated along said path for receiving the light from said light source means, support means supporting said light source means and photosensitive means at a location where smoke to be tested will pass across said path between said light source means and photosensitive means, so that the extent to which light is received from said light source means by said photosensitive means will be determined by the degree of opacity of the smoke flowing across the path of light travelling from said light source means to said photosensitive means, meter means for providing an indication of the opacity of the smoke, electrical means operatively connected with said photosensitive means and meter means for operating the latter in accordance with light received by said photosensitive means from said light source means to indicate at said meter means the extent of opacity of the smoke flowing across the path of light travelling from said light source means to said photosensitive means, and compensating means electrically connected with said electrical means and carried by said support means for responding automatically to fluctuations in light received by said photosensitive means from any source other than said light source means and for providing an automatic compensation for said fluctuations in any light received by said photosensitive means other than the light travelling from said light source means to said photosensitive means, so that said photosensitive means will respond only to variations in the intensity of light from said light source means to prevent said meter means from being influenced by any other light variations.

2. The combination of claim 1 and wherein said light source means provides light pulses of predetermined frequency and said photosensitive means responds to the amplitude of the light pulses for providing through said electrical means and meter means an indication of the opacity of smoke flowing between said light source means and photo-sensitive means.

3. The combination of claim 1 and wherein said compensating means includes a biasing lamp providing at least part of the light received by said photosensitive means from any source other than said light source means, said biasing lamp being connected by said electrical means to the output of said photosensitive means for maintaining a predetermined voltage offset at the output of said photosensitive means, said electrical means rebiasingsaid biasing lamp in response to fluctuations in light other than the light from said light source means to restore the predetermined voltage offset for maintaining constant any light other than the light from said light source means.

4. The combination of claim 3 and wherein said electrical means includes a direct-coupled amplifier and emitter-follower connected to said biasing lamp for maintaining automatically the predetermined voltage offset at the output of said photosensitive means.

5. The combination of claim 4 and wherein said photosensitive means is in the form of a silicon photo transistor.

6. The combination of claim 5 and wherein said light source means provides light pulses of predetermined frequency so that said photosensitive means responds to variations in the amplitude of the light pulses in ac cordance with the opacity of the smoke.

7. The combination of claim 6 and wherein said electrical means includes a band pass filter tuned to the frequency of the light pulses from said light source means.

8. The combination of claim 7 and wherein said electrical means also includes a holding circuit for storing a peak opacity reading.

9. The combination of claim 1 and wherein said support means is in the form of an open frame carrying said light source means and photosensitive means with the space therebetween open to the outer atmosphere for removably mounting said light source means and photosensitive means at the discharge end of an exhaust pipe of a motor vehicle on opposite sides of the path taken by the smoke issuing from the exhaust pipe, so that smoke issuing from the exhaust pipe will flow between the light source means and photosensitive means.

10. The combination of claim 9 and wherein said support means supports said light source means and photosensitive means for situating the path of travel of light from said light source means approximately six inches from the discharge end of the exhaust pipe.

11. The combination of claim 3 and wherein said biasing lamp of said compensating means is a tungsten biasing lamp.

12. The combination of claim 1 wherein said light source means includes a gallium phosphide lamp and a pulse generator operatively connected thereto for providing light pulses of predetermined frequency travelling along said path from said light source means to said photosensitive means. 

1. In a smoke meter, light source means for directing light along a predetermined path, photosensitive means situated along said path for receiving the light from said light source means, support means supporting said light source means and photosensitive means at a location where smoke to be tested will pass across said path between said light source means and photosensitive means, so that the extent to which light is received from said light source means by said photosensitive means will be determined by the degree of opacity of the smoke flowing across the path of light travelling from said light source means to said photosensitive means, meter means for providing an indication of the opacity of the smoke, electrical means operatively connected with said photosensitive means and meter means for operating the latter in accordance with light received by said photosensitive means from said light source means to indicate at said meter means the extent of opacity of the smoke flowing across the path of light travelling from said light source means to said photosensitive means, and compensating means electrically connected with said electrical means and carried by said support means for responding automatically to fluctuations in light received by said photosensitive means from any source other than said light source means and for providing an automatic compensation for said fluctuations in any light received by said photosensitive means other than the light travelling from said light source means to said photosensitive means, so thaT said photosensitive means will respond only to variations in the intensity of light from said light source means to prevent said meter means from being influenced by any other light variations.
 2. The combination of claim 1 and wherein said light source means provides light pulses of predetermined frequency and said photosensitive means responds to the amplitude of the light pulses for providing through said electrical means and meter means an indication of the opacity of smoke flowing between said light source means and photo-sensitive means.
 3. The combination of claim 1 and wherein said compensating means includes a biasing lamp providing at least part of the light received by said photosensitive means from any source other than said light source means, said biasing lamp being connected by said electrical means to the output of said photosensitive means for maintaining a predetermined voltage offset at the output of said photosensitive means, said electrical means rebiasing said biasing lamp in response to fluctuations in light other than the light from said light source means to restore the predetermined voltage offset for maintaining constant any light other than the light from said light source means.
 4. The combination of claim 3 and wherein said electrical means includes a direct-coupled amplifier and emitter-follower connected to said biasing lamp for maintaining automatically the predetermined voltage offset at the output of said photosensitive means.
 5. The combination of claim 4 and wherein said photosensitive means is in the form of a silicon photo transistor.
 6. The combination of claim 5 and wherein said light source means provides light pulses of predetermined frequency so that said photosensitive means responds to variations in the amplitude of the light pulses in accordance with the opacity of the smoke.
 7. The combination of claim 6 and wherein said electrical means includes a band pass filter tuned to the frequency of the light pulses from said light source means.
 8. The combination of claim 7 and wherein said electrical means also includes a holding circuit for storing a peak opacity reading.
 9. The combination of claim 1 and wherein said support means is in the form of an open frame carrying said light source means and photosensitive means with the space therebetween open to the outer atmosphere for removably mounting said light source means and photosensitive means at the discharge end of an exhaust pipe of a motor vehicle on opposite sides of the path taken by the smoke issuing from the exhaust pipe, so that smoke issuing from the exhaust pipe will flow between the light source means and photosensitive means.
 10. The combination of claim 9 and wherein said support means supports said light source means and photosensitive means for situating the path of travel of light from said light source means approximately six inches from the discharge end of the exhaust pipe.
 11. The combination of claim 3 and wherein said biasing lamp of said compensating means is a tungsten biasing lamp.
 12. The combination of claim 1 wherein said light source means includes a gallium phosphide lamp and a pulse generator operatively connected thereto for providing light pulses of predetermined frequency travelling along said path from said light source means to said photosensitive means. 